Effect of cosolvents on the precipitation polymerization of acrylic acid in supercritical carbon dioxide

The precipitation polymerization of acrylic acid (AA) in supercritical (SC) carbon dioxide with acetic acid and ethanol as the cosolvent were studied at 335 K in the range 12-17 MPa; 2,2'-azobis(isobutyronitrile) AIBN was used as the initiator. Analysis by viscosity measurement and differential scanning calorimetry (DSC) indicates that the cosolvents have a pronounced effect on the product molecular weight and glass transition temperature (T-g) Scanning electron microscopy (SEM) shows that the products are microparticles, and their sizes are affected by the structure and concentration of the cosolvents. A UV/Vis spectroscopic method was used to study the initiation rate of AIBN. The molecular weights of the products are closely related to the decomposition rate. (C) 2000 Elsevier Science Ltd. AII rights reserved.